Abstract
NOx reduction is a major challenge for the OEMs with the impending BS6/EU6 emission norms. Lean NOx Trap (LNT) is one of the technologies which can help achieve the targets. With adsorbers such as barium oxide, the LNT is able to trap the NOx coming out of the engine, running in lean mode, in the presence of an oxidation catalyst like Platinum. As the substrate gets saturated due to its finite storage capacity, it has to be regenerated. For this purpose, a rich pulse is released for a small duration which helps to restore the LNT and release the trapped NOx by converting it into nitrogen in the presence of a reducing catalyst like Rhodium. Understanding this LNT behavior and ascertaining the tail pipe emissions in Real Driving Emission (RDE) cycles is challenging until the finally calibrated vehicle level prototype is available. To this purpose, a numerical model is developed in Simulink which simulates the LNT behavior to provide an estimate of its NOx conversion efficiency for different drive cycles. This numerical model uses the LNT efficiency maps, storage capacity maps, essential engine operating conditions for regeneration, and transient temperature effects which can be obtained from engine dynamometer. From these inputs, the model gives an estimate of tailpipe NOx emissions and fuel penalty for regenerating the LNT. A good correlation was found when compared with testing results for NEDC cycle. This numerical simulation, hence, can reduce the product development time considerably by providing an estimate of crucial parameters such as feasibility of LNT for the engine - vehicle combination, determination of suitable size of the LNT, conformity to the emission norms such as BSVI etc.